Method for forming metal balls



P 1944- s. E. BRENHOLTZ METHOD FOR FORMING METAL BALLS 2 Sheets-Sheet 1Filed July 14, 1941 INVENTI] R EEBRENHIJLTZ G. E. BRENHOLTZ 2,358,378

METHOD FOR FORMING METAL BALLS Sept. 19, 1944.

Y 2 Sheets-Sheet 2 Filed July 14, 194].

FIG-.11.

Z RU DU m T M NN D w R A W5 D @L I I 7 Z Patented Sept. 19, 1944 METHODFOR. FORMING METAL BALLS George E. Brenholtz, Hamilton, Ontario, CanadaApplication July 14, 1941, Serial No. 402,408

8 Claims.

This invention relates to a method for forming metal balls.

The general method of making metal balls in use at the present time iscarried out by a machine of the open die type wherein two identicalhemispherical die cavities are reciprocated toward each other with ametal slug disposed between them so as to compress the slug into theform of a sphere when the dies meet. One particular disadvantage of thismachine is that since the die cavities must be completely filled, excessmetal must be permitted in the slug which has the result that an equatorring is formed on the ball. Moreover, in order to discharge the ballfrom the die cavities as they are moving away from each other, a slidingplunger is used to contact the ball which has the result of flatteningthe ball at its pole.

In some instances where a perfect sphere is required such as in the caseof ball bearings, it is necessary to subject the balls to furtherfinishing operations, trimming for the equator ring and grinding thesphere, thus requiring two or more operations.

A further method which is employed in forming balls makes use of spiralpassageways formed in cooperating rolls which operate on the principleof a worm and draw in to the passageways bar stock from which lengthsare cut to form slugs and such slugs subjected to a progressive formingoperation as they pass along the spiral throughout the length of therolls. A particular disadvantage of this method is that the collarsbetween sections of the spiral passage in the rolls have a tendency topull the end edges of the slugs downwardly and upwardly so as in eiiectto fold some of the metal over, giving the ball a cabbageleaf efiectwith the result that such leaves subsequently flake oil and are objectedto since they clog the screens of the ball mills and the like.

A further disadvantage of both methods above referred to and in mostball forming methods is that perfect synchronization of the moving partsof the mechanism and the fitting of the slugs from which the balls areformed is required and this necessarily requires the use of timingmechanism.

It is an object of the present invention to avoid the disadvantage ofthese prior types of machines by providing a method through which theballs can be formed into a perfect sphere in one continuous operationwhich when formed will not be subject to the objections of equator ring,fiat pole or cabbage-leaf effect.

A further object of the invention which naturally follows is theproduction of metal balls economically.

A still further object of the invention is to provide a method of thischaracter through which such balls may be produced in volume in acomparatively short space of time.

A still further object of the invention is to provide a method throughwhich the mechanism employed for producing the balls may be quicklyadapted to produce balls of different sizes as may be required. Withthese and other objects in view the method generally comprises forgingmetal balls from slugs by causing each slug to travel along an extendedpath, preliminarily subjecting the slug to the pressure engagement ofdeforming dies at four points of its surface to deform the sluginitially, and finally subjecting the deformed slug to the pressureengagement of arc-shaped dies at three points only, on its surfacethroughout the remaining portion of its travel, the polar zones of thegradually forming sphere being formed by two die surfaces and theintervening circumferential zones being formed by the other or remainingdie. The method preferably provides for the formation of metal spheresor balls in one continuous operation and includes a rotary forgingoperation wherein the axis of the rotation of the ball being formedremains parallel substantially throughout its travel through the formingdies and preferably the axis of rotationis finally swung so as to assumea position substantially at right angles to its normal position during afinal finishing step over a minor portion of its travel through thedies.

The various features of the method will be clearly understood byreference to the following detailed specification taken in conjunctionwith the accompanying drawings.

In the drawings:

Fig. 1 is a schematic side elevation of rotary and stationary dies andtheir preferred positioning for forming metal balls.

Fig. 2 is a vertical section taken through the centre of the rotary diein advance of the stationary die.

Fig. 3 is a side elevation of die sections making up the stationary die.

Figs. 4 to 9 are sections taken along the lines Fig. 11 is a viewsimilar to Fig. 10, but showing an enlargement in both sides of thegroove of the die and also illustrating mechanical means for causing theballs being formed to swing from their normal axis of rotation.

Fig. 12 is' a transverse section taken through the cooperating rotaryand stationary dies at a point adjacent to the entrance to the diepassageway and showing a metal slug positioned as it begins travelbetween the dies.

Fig. 13 is a transverse section taken through the cooperating dies at a,point just adjacent to the discharge and showing a ball practicallyfinished by also illustrating the extent of contact between the surfaceof the ball and the forming surfaces of the dies.

Fig. 14 is a fragmentary detail of the apparatus illustrating anextension which may be applied to increase the length of the path oftravel of the slugs when forming balls of large diameter, and

Fig. 15 is a schematic illustration of the three point contact betweenthe ball being formed and the die faces in the final stages ofprocessing.

Referring to the drawings, a preferred general type of apparatus isillustrated in Fig. 1 wherein A indicates a rotary forging die and Bindicates a cooperating stationary forging die which may be mounted onany suitable stationary framework H). The stationary die B is arcuate inelevation and is designed as shown to lie parallel to a correspondingarc of the rotary die. The rotary die is formed with a circumferentialgroove ll of constant cross section while the stationary die is formedwith a corresponding groove I! of changing cross section along itslength as will appear in detail hereinafter. The grooves of these openfaced dies are, as clearly shown in Fig. 2 and Figs. 12 and 13, disposedin opposed relation to one another so as to form therebetween a channell3 over an extended arcuate path through which metal slugs will passprogressively as they are formed from their initial shape into that or aball or sphere.

The slugs C are shown in Fig. 12 are preferably cut from bar stock of adiameter and length such that they will provide suilicient metal as toform a perfect sphere of given size after passing through between thedies A and B. These slugs may be sheared to length by suitablyreciprocating shearing knife ll reciprocated by suitable mechanism (notshown) and preferably has an arcuate cutting edge I! designed to contactwith the bar stock which is preferably fed horizontally through themechanism in the path of the knife II.

The slugs as they are cut may pass along a suitable table which may bein the form of a guideway, cut slugs being disposed contiguous to oneanother on the table and pushed one by the other through suitablemechanism reciprocating in conjunction with the knife ll until theforemost slug passes through the point of entry of the channel l3between the dies A and B, a slug being fed into the machine each timeone is cut from the bar stock.

The length of the guideway or channel I! will depend upon the size ofthe'balls being formed and the amount of processing required andprovision may be made to increase the length of the channel by employingadditional parts as will be referred to hereinafter. However, I preferthat the discharge end of the channel [3 will, where possible,coincide-with the centre of the rotary die and at the bottom of therotary die as clearly shown in Fig. 1.

A salient feature of the invention resides in the contour andarrangement of the rotary and stationary dies A and B. The stationarydie may be formed in one piece as clearly shown in Figs. 4 and9 or maybe formed in two parts as shown in Figs. 12 and 13. In either case,however, the contours of the groove I2 which is formed by both sides ofthe die will be the same.

The stationary die at the inlet end is formed with a fiat base I6 andpreferably of a width slightly wider than the length of the slug so asto accommodate the rough edges that may be 'presenton the slug. The sidewalls I! of the groove at this point are preferably fiat and slopedinwardly to the base It so that the slug when received will beaccurately disposed with its side wall lying on the fiat base so that itmay be caused to roll along the fiat base IS. The groove generallyretains this cross sectional shape for a short. distance,to start therolling motion of the slug during which period, the surface of thegroove ll of the rotary die A commences a preliminary deformingoperation which will be referred to hereafter.

The groove requires two working surfaces so that as a means ofeliminating any possible extra friction it is centrally divided eitherby a trough or channel l8 or may be formed in two separate sections witha dividing channel l9 such as shown in Figs. 12 and 13. On the otherhand it may have both a trough l8 over a portion of its extent and bedivided over another. At the end of the flat base IS the contour of thegroove gradually changes into a gradually increasing arcuate deformingsurface which is part of the true are of the sphere finally to beformed.

The deforming surface starts on each side of the groove from the edge ofthe trough l8 or the channel H) as the case may be, gradually increasinguntil in the final stages of processing, the arcuate deforming surfacesof the groove I! each approximate one-sixth of the complete circlecorresponding to the diameter of the ball being formed.

The gradual formin of the slug into a sphere by means of this gradualchange in the contour of the groove 12 of die B in conjunction with theconstant shaped groove II in the rotary die will be appreciated byreference at this point to the shape of the groove of the rotary die. Inthis connection reference is made to Fig. 12 wherein it will be seenthat the centre part of groove I I is formed as an arc to the extent ofone-sixth of the true are of the sphere being formed and in some casesslightly more than one-sixth of this distance, such are being indicatedat Ila extending between the broken lines a-b. The remaining portion ofthe groove on each side of the arc portion Ha is gradually flared out asat H b to meet the width of the opening of groove I! in the stationarydie and in fact the shape of the marginal portions of g Jove, llsubstantially corresponds to the cross sectional shape of groove l2 atthe point shown by section of Fig. 5. i The base I6 of the stationarydie and part of the curved walls of the groove are ragged or scored soas to provide a rough surface which will prevent slippage as indicatedat 20, Figs. 10 and 11. correspondingly the fiared portion llb of thegroove II is ragged or scored throughout the whole circumference of thedie. These ragged surfaces as well assist in causing the slug to rotateabout its axis so that as the slug passes between the dies it issubjected to a rollin forging operation.

As the rotary die A rotates the slug which has just entered thepassageway I3 as shown in Fig. 12 will be caused to rotate and itscorners will be subjected to the pressure engagement of the flaredportion of the groove II clearly shown in Fig. 12 where pressure contactis just beginning to commence. This pressure contact is caused by thecontour of the groove l2 in the lower stationary die. As the slug movesalong the passageway l3 and reaches a point in the passagewaycorresponding to that where the cross section of Fig. 5 occurs on lowerdie B, the corners of the slug have been deformed substantially to theextent shown in Fig. 5 and at this point the inner portions of the diegroove surfaces have been formed with a small portion 2| of the true arcof the sphere being formed, (shown between broken lines cd) while theoutwardly and upwardly flared surfaces 22 on each side of the arcportion 2| are such as to lessen the depth of groove l2 at this point.As a result, therefore, it will be seen that the metal of the slug isbeing caused to flow gradually upwardly and downwardly, a portion of thetrue arc of the sphere being formed by the arcs 2I while at the sametime a further portion of the arc of the true sphere is being formed onthe slug by the arcuate portion I la of rotary die A as the metal flowsupwardly and downwardly.

As the slug progresses through channel I3 and reaches a point where thecross section of Fig, 6 is taken, the arc 2| as shown in Fig. 5 nowbecomes are 23, (shown between broken lines e-f) which is substantiallytwice as long.whereas the flared portions 22 of groove I2 are such thatthe cross sectional area of the groove on each side of are 23 has beenlessened. In view of this, the metal is caused to flow to a greaterextent upwardly and downwardly and while a greater portion of the trueare of the final sphere is formed by the arcs 23 of the die B, a greaterportion of the arc of the true sphere is being formed on the slug by thearcuate portion Ila of the rotary die A.

The cross sections of the die B as shown in Figs. 7, 8 and 9, discloseprogressively increased arcuate surfaces 25, 26 and 21 (occurring between the broken lines g--h, i-k, l-m respectively) until at 21 aboutfour-fifths of the true arcuate surface of the lower die sections isattained, the final arcs (Fig. 13) corresponding as previously stated tosubstantially one-sixth in each case of the circumference of the spherebeing formed. The gradual formation of the slug can be seen from Figs. 5to 9 and the finished sphere between the dies A and B, is shown in Fig.13. In this instance it will be noted that the full arcuate surfaces ofthe stationary die B in efiect overlap the full arcuate surface I la ofthe rotary die A so that the three points of contact which have beengradually enlarged in the case of die B, substantially to correspondwith the constant full size of are I la in die A, assure that a perfectsphere is formed by the time that the slug is discharged.

As noted by referring to the die cross sections, the edges of the diesections of die B are gradually rounded at their inner edges as at 28(see Figs. 8, 9, 13) while the outer edges are also gradually rounded asat 29 so as to avoid sharp edges which might have a tendency to creasethe Ill slug being formed and by reason of this and the fact that atleast upper die arc Ila is greater than one-sixth of the circumferenceof the sphere, the sphere is kept from being marked by the dies,

The lower die B may be formed in a series of segments 30 as shown inFig. 3, so that individual segments may be adjusted laterally toaccommodate wear, and also in the case of the first part of the die soas to increase the size of the die passageway, if necessary, i order tomake certain that slugs which have become crooked or distorted throughhot shearing may be accurately centered to lie on the die base I6. Thelower die, in this instance, would therefore preferably be split in twosections and as many segments as desired may be employed and varying inlength if necessary,

As the slug is gradually formed into a sphere as above described throughthe rolling forging operation, the slug rotates about its axissubstantially parallel with the path of travel of the slug. In order toavoid the possibility of small cone peaks at the end of the axis ofrotation it is desirable to change the position of the slug towards theend of its passage between the dies so that it may be caused to rotatesubstantially at right angles to its normal axis of rotation. To thisend a part of the groove of the lower die section may be enlarged asindicated at 3| (see Fig. 10) which would have the effect of relievingthe pressure of the die on the slug at one side and through the frictionset up by the contact of the ball being formed with the rotary die andwith the other side of the lower die, the tendency is to spin the ballcausing it to change its positions so that the ends of normal axis ofrotation or, in other words, the polar zones of the sphere would bepositioned so that they would be engaged by the arcuate portion Ila ofdie A, thus to eliminate any possibility of peaks. Alternatively, thedie sections of stationary die B may be enlarged as at 32 and 33 and amechanically operated friction wheel 34 may be positioned below the diesections between the enlargements 32 and 33 so as to contact the spherebeing formed. The friction wheel 34 is disposed to rotate in a directionat right angles to the normal axis of rotation of the sphere beingformed so that it would cause the sphere being formed to rotate at rightangles to its normal axis of rotation, thus assuring that during theremaining part of its passage between the dies it would be caused torotate substantially at right angles to its normal axis of rolationduring its previous passage between the res.

As previously indicated the length of the stationary die andconsequently the extent of the path of travel of the slug through thedies will depend upon the size of the sphere to be formed. This might beextended by adding to the structure in Fig. 1 an extension 35 to thestationary die and feeding slugs between the dies at a point higher thannormal. Alternatively, the sphere might be formed in two operations, thefirst consisting in shaping the slug up to a point shown by the lowerdie shape in Fig. 7, and completing the final shaping as shown in Figs.8, 9 and 13 in a second operation. In other words, two similar machineswould be employed.

From the foregoing it will be appreciated that the method described willattain the objects I have set out. The elimination of the necessity forsynchronous feed and synchronization of the dies permits feeding ofslugs to the machine as fast as the shearing knives can shear them.Furthermore, while the method and apparatus tends to avoid slippage itwill be noted that if slippage were to occur in the case of any slugspassing through the dies, nothing disadvantageous would result as theslug would merely receive a little more processing whereas in thesynchronized machine the machine would jam or the slug would be spoiled.

Asalient feature of the invention, as will be realized from theforegoing, lies in the fact that the dies are so shaped and arrangedthat friction is reduced to a minimum. In this instance, it will beappreciated that throughout the passage of the slug between the rotaryand stationary dies. there are very few points of contact between theslug and the stationary die and the rotary die which are similar, and inthe. flnal stages of processing the ball being formed is con.. tacted bythe dies at three points only, the point of contact with the rotary diebeing positioned between the points of contact with the stationary dieso that the speed of rotation of the ball in terms of its contact withthe rotary die is not impeded as would be the case were it contacted bycontinuous semi-circular grooves.

It should be appreciated that the changing in cross sectional shape ofthe die faces of the stationary die is gradual throughout and that theillustration of the change in shapeof the slug illustrated in Figs. 4 to9 and 13 are approximations of the shape as the slug reaches that pointin the die, with other changes in shape occurring at intermediatepoints.

The apparatus involved for carrying out the method is of the simplesttype and, of course, may be varied in general construction to providespecial feeding means, shearing means, or the like. a

What I claim as my invention is:

1. In the method of forging metal balls in one continuous operation thesteps of causing metal slugs to travel successively through an extendedsingle arcuate path and subjecting each slug to the pressure engagementof dies at three points only during a substantial portion of theirtravel while gradually forging the slug into a sphere.

2..The method of forging metal balls in one continuous operation whichcomprises causing metal slugs to travel successively through an extravelof the slugs are gradually increased.

4. The method of forging metal balls in one continuous operation fromelongated metal slugs which comprises causing each slug to travelsuccessively through an extended single arcuate path parallel to itslongitudinal axis, preliminarily subjecting each slug to the pressureengagement of deforming dies at four points to deform them while causingthem to rotate about its axis and then subjecting each slug to thepressure engagement of dies at three points only during the remaining orfinal portion of their travel while gradually forging each deformed sluginto a sphere.

5. The method as claimed in claim 4 in which the position of each slugin the path of travel is changed towards the end of the remaining orfinal portion of their travel to change the axis of rotation, of eachslug.

6. The method of forging metal balls in one continuous operation whichcomprises initially shearing cylindrical bar stock to form a metal slughaving the planes of its ends substantially at right angles to its axispassing the metal slug through between three circumferentially spacedapart arcuate die surfaces of frictional character and jointly arrangedin one single arcuate path and gradually increasing the arc of two ofthe surfaces to overlap the third surface while gradually forming theslug into a sphere.

'7. The method of forging metal balls in one continuous operation whichcomprises initially shearing cylindrical bar stock to form a metal slughaving the planes of its ends substantially at right angles to its axispassing the slug between three circumferentially spaced apart arcuatesurfaces of frictional character and jointly arranged in one singlearcuate path and in pressure contact therewith, forming the polar zonesof the sphere from two of said surfaces and the equatorial zones of thesphere from the remaining arcuate surface.

8. The method of forging metal balls in one continuous operation whichcomprises initially shearing cylindrical bar stock to form a metal slughaving the planes of its ends substantially at right angles to its axispassing the slug between three circumferentially spaced apart arcuatesurfaces of frictional character and jointly arranged in one singlearcuate path, causing said slug vto rotate in pressure contacttherewith, about an axis forming the polar zones of the sphere from twoof said surfaces and the equatorial zones of the sphere from theremaining arcuate surfaces and changing the position of the slug duringthe final stage of contact with said surfaces to cause it to rotate atsubstantially right angles to said axis whereby polar zones of thesphere are brought into pressure contact with the remaining arcuatesurface. 7

GEORGE E. BRENHOLTZ.

